Upgrade to windows 11 Pro from unlicensed Home version

    In my experiences, the long and short of your issue is that the official in-place upgrade from Win11 Home to Win11 pro will I believe require an activated Win11 Home installed.  As you stated, you apparently have an unlicensed version installed currently of Win11 Home, which I believe the reason your upgrade process is failing.

   That being said.... what now, right?  Well, there are two ways that I know will work where you won't have to do any reformatting, etc.  Those two methods are:

1. The officially Microsoft-recommended method:

      Simply find an outlet vendor of MS Windows licenses and purchase a Win11 Home license at the most affordable rate you can find.  After getting your Win11 Home product key you purchase.... simply go back to the Windows activation settings within your unlicensed Windows 11 Home and select to "change" adding the newly purchased product key.  After it being accepted by the system, make sure to reboot BEFORE trying to start the in-place upgrade process to Win11 Pro.  If you complete these steps, you will be fully legal with your upgraded Windows 11 and able to be fully supported through official Microsoft technical support.

      2.  The "Other" Route method (not officially supported):

      While I won't disrespect Microsoft specifically here, I will make note to you that simply activating your unlicensed Win11 Home through "other non-Microsoft alternative means" and then restarting your in-place Win11 Pro upgrade will also achieve your sought-after end result.  I will only suggest that if you choose this route that you should use available public search engines to find the process methodology to do so as I can't imagine Microsoft allowing such to be detailed on their own public forums and doing such would additionally be disrespectful of me.

     Hope this all helps you reach your intended end result and either option will.  God speed and good efforts forward😉

Sincerely,

Paul Scallan Jr